Spatial focusing of electrical resistivity surveys considering geologic and hydrologic layering

Alex Furman, Ty P.A. Ferré, Gail L. Heath

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

Electrical resistivity tomography (ERT) has shown great promise for monitoring transient hydrologic processes. One advantage of ERT under those conditions is the ability of a user to tailor the spatial sensitivity of an ERT survey through selection of electrode locations and electrode combinations. Recent research has shown that quadripoles can be selected in a manner that improves the independent inversion of ERT data. Our ultimate interest lies in using ERT data along with measurements from other sensors, which typically can provide high-quality data from shallow regions of the subsurface, in a joint inversion. As a result, we do not consider the selection of quadripoles specifically for inde-pendent ERT inversion. Rather, we present an approach to focusthe spatial sensitivity of ERT surveys in specificsubsurface regions with the assumption that those data, when interpreted along with other measurements that are sensitive to those regions, will lead to more complete hydrologic characterization. Because we are interested in monitoring rapid processes, our approach is designed to efficiently identify optimal quadripoles. This is achieved by separating the optimization from the inversion grid, significantly reducing computational effort. We extend our previous work to consider the use of both surface and borehole ERT electrodes and to consider the impacts of horizontally layered electrical conductivity conditions. Results confirm the ability of the method to focus survey sensitivity while showing the importance of incorporation of prior knowledge of the subsurface electric conductivity structure in designing optimal ERT surveys.

Original languageEnglish (US)
Pages (from-to)F65-F73
JournalGEOPHYSICS
Volume72
Issue number2
DOIs
StatePublished - 2007

Keywords

  • Electrical conductivity
  • Hydrology
  • Terrestrial electricity

ASJC Scopus subject areas

  • Geochemistry and Petrology

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